Environmental credit trading programs have gained traction for pollutants like carbon emissions, at least in concept. Is water quality trading the next frontier? The mechanism offers the possibility of more flexible and cost-effective water quality control, but in contrast to some environmental credits, markets have struggled to gain momentum.

Water quality trading markets allow the operators of point sources of water pollution — such as sewage treatment plants or factories — to offset that pollution by purchasing credits representing reductions elsewhere. Just as the purchase of a carbon offset gives its buyer credit for reducing their carbon footprint, a water quality trading market allows participants to buy and sell the credit for reduction of water pollution into a given water body.

Trading is a tool that may be well-suited to address the evolving nature of water pollution in the United States.

“The Clean Water Act was written at a time when the major pollution in our waterways was coming from pipes,” said Kristiana Teige Witherill, clean water project manager at the Willamette Partnership, a nonprofit focused on market-based conservation in the American West. “Today, depending on what watershed you’re looking at, 80 to 90% of pollution is coming from non-point sources, not coming from the end of a pipe.”